1. Field of the Invention
The present invention relates generally to heat sinks used to cool electronic modules, and, more particularly, to liquid heat sinks used to cool such modules.
2. Description of the Related Art
When the surface heat flux from a module exceeds a critical value, a heat sink is required to increase the surface area for heat transfer. This can be done by the use of either a conventional solid heat sink, such as an aluminum heat sink, or a liquid heat sink. When more than one module requires a heat sink and space restricts the use of conventional aluminum heat sinks, a liquid heat sink can be used to transfer heat from hot components to a cold plate.
Conventional liquid heat sinks are enveloped to contain the liquid, and this envelope produces the following restrictions:
1) A pressure has to be maintained between the heat dissipating components and the envelope to decrease the thermal contact resistance.
2) The card, or printed circuit board, on which modules are attached has to be specially supported to maintain sufficient pressure to ensure heat transfer efficiency. This requires a card stiffener and flexible card supports to allow the card to move with the thermal expansion of the liquid. Without this special support mechanism, the circuit card would flex during thermal cycling, with possible damage to lands and component/card interfaces.
3) The liquid envelope restricts complete surface coverage of the component by the liquid.
What is needed is a liquid heat sink that retains the advantages of such heat sinks, but which avoids most, if not all, the problems of the prior art liquid heat sinks.